diff --git a/Makefile b/Makefile
index 08b0119..cd7804c 100644
--- a/Makefile
+++ b/Makefile
@@ -3,12 +3,14 @@ ODE_CFLAGS = `pkg-config --cflags ode`
 ODE_LIBS = `pkg-config --libs ode`
 AMX_CFLAGS = `pkg-config --cflags amx`
 AMX_LIBS = `pkg-config --libs amx`
+GL_CFLAGS = `pkg-config --cflags gl`
+GL_LIBS = `pkg-config --libs gl`
 
 AR = $(TARGET_PREFIX)ar
 CC = $(TARGET_PREFIX)gcc
-CFLAGS = $(ODE_CFLAGS) $(AMX_CFLAGS)
+CFLAGS = -D_DEFAULT_SOURCE $(ODE_CFLAGS) $(AMX_CFLAGS) $(GL_CFLAGS)
 LDFLAGS =
-LIBS = $(ODE_LIBS) $(AMX_LIBS)
+LIBS = $(ODE_LIBS) $(AMX_LIBS) $(GL_LIBS)
 
 EXEC =